This blog post will launch a multi-part series analyzing the benefits of eating a diet replete with healthy types of fat. We will look at the difference between healthy and unhealthy fats, why high fat diets are better for weight loss, the health benefits of eating diets high in healthy fats and an overview of numerous studies that have been done over the last century and what they can tell us about the optimal ratio of macronutrients (carbohydrates, fat, and protein) in our diet.
This week, we will take a peak into recent research that demonstrates the metabolic advantage of eating a diet higher in fat and lower in carbohydrate.
First, a bit of history -
In the 1960's, before we began suffering from obesity of epidemic proportions, Americans ate about 40% of our calories from fat and another 40% from carbohydrate sources. But, under the influence of some faulty science, the USDA published guidelines in 1977 recommending a diet higher in carbohydrates, primarily from grains, and lower in fat. Americans dutifully complied, reducing fat consumption to 33% of calories and increasing carbohydrate consumption to 55%. We have increased our fruit and vegetable consumption by 17 percent and our grain consumption by 29 percent. Interestingly, in this same time period, Americans also began exercising more.
In short, we cut out fat in our diet and replaced them with carbohydrates. The American breakfast menu shifted from bacon and eggs to cereal, oatmeal, and low fat yogurt. We replaced animal fats from lard, butter, and tallow with vegetable oil, a product that didn't exist in our diets a century ago, and now comprises about 10% of calories in our modern diets. The results of this dietary shift have been devastating.
Now, the research:
Dr. David Ludwig and his team at the Harvard School of Public Health conducted a study comparing different ratios of carbohydrates to fat in the diet, splitting participants into a high carb group (60 percent of calories from carbs), a moderate carb group (40 percent carbs), and a low-carb group (20 percent carbs).
As carbohydrate consumption in the diet decreased, metabolism increased, resulting in greater energy expenditure and calorie burn. Participants in the low carb group burned between 250 and 400 calories a day more when compared to the high carb group. Over time, the increased efficiency in energy metabolism can lead to significant weight loss, especially considering the fact that diets higher in fat tend to curb hunger and cravings more effectively compared to diets higher in carbohydrates.
Dr. David Ludwig, the lead investigator, shared that the results of the study "suggest that what we eat — not just how much — has a substantial effect on our metabolism and thus how much weight we gain or lose."
We have been told for decades that in order to lose weight, we need to burn more calories than we eat. While at a 30,000 foot level, this appears to be true, the reality is much more nuanced than this simple thermodynamic equation. To provide a simple example, I think no one would argue which is healthier option between the following two foods:
1. Eating 100 calories of Alaskan, wild-caught salmon
2. Eating 100 calories of a snickerdoodle cookie
Now the interesting question is -- let's suppose my body burns an average of 3000 calories per day. Which diet would I be more likely to lose weight on?
1. 3200 calories per day of Alaskan, wild-caught salmon
2. 2800 calories per day of snickerdoodle cookies?
Conventional wisdom points toward the second diet; however, I would argue that I would lose more weight on the first diet and that the second diet will likely cause me to gain weight. Why is that? We'll see in next week's blog post.
This article will appear in the 7th edition of my newsletter, "5 Big Ideas to Upgrade your Health."
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